In the manufacturer of crosslinked foamed profiles, a foam formulation with a fast cure rate helps to control pore size. A high cure rate also helps to achieve a fast crosslinking of the skin of the profile, and for the formation of a foam with small pores sizes (lower than 500 microns). To achieve these results, conventional practice uses EPDM grades with 5-ethylidenenorbornene (ENB) levels above 7.5 weight percent. However, high levels of ENB increase the cost of the interpolymer, since the ENB is an expensive raw material. In addition, interpolymers containing high levels of ENB result foam formulations with short scorch time, which leads to processing problems.
There is a need for EPDM-based formulations, which contain relatively lower levels of ENB, and which have cure rates similar to formulations containing higher ENB interpolymers. There is a further need for crosslinked foams that can be formed from formulations that have longer scorch times. These needs and others have been met by the following invention.